PE Environmental cheat sheet

NAAQS primary standards: PM2.5 annual 9.0 µg/m³ and 24-hour 35 µg/m³; PM10 24-hour 150 µg/m³; ozone 8-hour 0.070 ppm; NO2 annual 53 ppb and 1-hour 100 ppb.

SO2 1-hour standard is 75 ppb; CO standards are 35 ppm (1-hour) and 9 ppm (8-hour); the lead standard is 0.15 µg/m³ as a rolling 3-month average.

Ozone compliance uses the 4th-highest daily maximum 8-hour concentration averaged over 3 years; 24-hour PM2.5 compliance uses the 3-year average of the 98th percentile of 24-hour values.

Gaussian plume: C = Q/(2πuσyσz)·exp(−y²/2σy²)·[exp(−(H−z)²/2σz²) + exp(−(H+z)²/2σz²)], where H is effective stack height (physical height plus plume rise).

Deutsch equation for electrostatic precipitators: η = 1 − exp(−wA/Q), with w = particle drift velocity, A = total collection plate area, Q = gas volumetric flow.

Unit conversion: mg/m³ = ppm × MW / 24.45 at 25 °C and 1 atm (use 22.414 at 0 °C); one lb-mol of ideal gas occupies 379.5 ft³ at 60 °F and 1 atm.

Emission estimate: E = A × EF × (1 − ER/100), where A is activity rate, EF is the emission factor (e.g., lb/ton, lb/10³ gal), and ER is percent control efficiency.

Pasquill-Gifford stability classes run A (most unstable) through F (most stable); class F with light winds produces the highest ground-level impact at long downwind distance.

BOD exerted at time t: BODt = L0(1 − e^(−k1t)) with k1 in base e; typical municipal wastewater k1 at 20 °C is 0.15–0.30 per day.

Streeter-Phelps oxygen sag: D = (k1L0/(k2−k1))(e^(−k1t) − e^(−k2t)) + D0e^(−k2t), where D is the deficit below saturation and k2 is the reaeration coefficient.

NPDES secondary treatment limits: 30 mg/L BOD5 and 30 mg/L TSS as 30-day averages, with at least 85% removal of each (40 CFR 133).

TMDL = ΣWLA + ΣLA + MOS; the margin of safety absorbs uncertainty between pollutant loading and the receiving-water response.

Stokes' law for discrete particle settling: v = g(ρp − ρw)d²/(18μ), valid for laminar settling with particle Reynolds number below about 1.

Disinfection: CT = residual disinfectant concentration (mg/L) × contact time (min); required CT increases with target log inactivation and decreases with higher temperature.

Activated sludge: F/M = (Q·S0)/(V·X); low F/M favors nitrification and lower sludge yield but requires larger aeration volume. MCRT = solids in system ÷ solids wasted per day.

Drinking water MCLs: nitrate 10 mg/L as N, arsenic 10 µg/L, fluoride 4.0 mg/L, lead action level 0.015 mg/L, copper action level 1.3 mg/L.

RCRA hazardous waste characteristics: ignitability (flash point below 60 °C), corrosivity (pH ≤ 2 or ≥ 12.5), reactivity, and toxicity as measured by the TCLP.

Generator categories: very small quantity generator under 100 kg/month, small quantity generator 100–1000 kg/month, large quantity generator 1000 kg/month or more; acute hazardous waste uses a 1 kg/month threshold.

On-site accumulation without a permit: large quantity generator 90 days; small quantity generator 180 days and no more than 6000 kg on site; very small generators have no time limit if quantity limits are met.

Landfill gas is roughly 50% methane and 50% carbon dioxide with trace VOCs; methane is explosive at 5–15% by volume in air, so extraction and migration controls are required.

Hazardous waste incinerators must achieve 99.99% destruction and removal efficiency for principal organic hazardous constituents; dioxin-listed waste requires 99.9999%.

TCLP (40 CFR 261.24): a 100 g sample is extracted with 2 L of extraction fluid, and the leachate is compared with toxicity characteristic limits (e.g., lead 5 mg/L).

Subtitle D MSW landfill design (40 CFR 258) requires a composite liner of compacted clay plus geomembrane, a leachate collection and removal system, and financial assurance.

Universal wastes - batteries, mercury lamps, mercury-containing equipment, certain pesticides, and aerosol cans - may be managed under reduced handling requirements.

CERCLA sequence: preliminary assessment/site inspection → Hazard Ranking System scoring and possible NPL listing → remedial investigation/feasibility study → record of decision → remedial design/remedial action → operation and maintenance.

Phase I ESA (ASTM E1527) is non-intrusive: records review, regulatory database search, site reconnaissance, and interviews to identify recognized environmental conditions.

Retardation: R = 1 + (ρb/θ)·Kd with Kd = Koc × foc; contaminant velocity equals seepage velocity divided by R.

Darcy's law: q = −K(dh/dL), where q is specific discharge; seepage velocity v = q/ne, with ne the effective porosity; hydraulic gradient is dimensionless (ft/ft).

DNAPLs (PCE, TCE, creosote) sink below the water table and pool on low-permeability layers; LNAPLs (gasoline, benzene) float on the water table and smear across the capillary fringe.

One-dimensional advection-dispersion with decay: ∂C/∂t = D(∂²C/∂x²) − v(∂C/∂x) − λC; applying retardation divides both v and D by R.

Remedy selection: pump-and-treat for dissolved plumes, SVE for vadose-zone VOCs, air sparging for saturated-zone VOCs, ISCO for source destruction, thermal for low-permeability sources, and MNA where natural attenuation is demonstrable.

VOC soil sampling: collect rapidly in sealed containers with zero headspace; EPA Method 5035 uses methanol or sodium bisulfate preservation for low-concentration samples.

Cancer risk = CDI × SF for ingestion/dermal or intake × IUR for inhalation; EPA's acceptable individual risk range for cleanup is 1×10⁻⁶ to 1×10⁻⁴.

Non-carcinogenic effects: HQ = CDI/RfD (or concentration/RfC); the hazard index is the sum of HQs, and HI > 1 indicates potential adverse health effects.

CDI_ingestion = (C × IR × EF × ED)/(BW × AT); for carcinogens AT = 70 years × 365 days, while for non-carcinogens AT = ED × 365 days.

Dermal intake = (C × SA × AF × ABS × EF × ED)/(BW × AT), where SA is exposed skin area, AF is soil-to-skin adherence, and ABS is the absorption factor.

OSHA 1910.120 (HAZWOPER): 40 hours of initial training plus 3 days supervised field experience for general site workers; 24 hours for workers limited to low-risk areas.

Occupational limits are distinct: PEL (OSHA, legally enforceable), TLV-TWA (ACGIH, advisory), REL (NIOSH, advisory), and IDLH (immediately dangerous to life or health).

Hazard index should be calculated separately for each target organ when multiple chemicals produce the same health effect, rather than summing across all endpoints.

Inhalation RfC (mg/m³) converts to an inhalation RfD (mg/kg-day) by multiplying by the assumed inhalation rate and dividing by body weight, typically 20 m³/day ÷ 70 kg.